Urine sugar testing



1958 w. M. FOWLER URINE SUGAR TESTING Filed Jan. 15, 1955 INVENTOR:

AM FOWLER i 3 i ATT'Ys WILLI BY I Patented Dec. 23, 1958 URINE SUGAR TESTING William M. Fowler, Oak Park, 111., assignor to Chicago Dietetic Supply House, Inc., Chicago, 11]., a corporation of Illinois Application January 13, 1955, Serial No. 481,587

7 Claims. 01. 23-230 This invention relates to urine sugar testing, and more particularly to the type of testing which by virtual necessity is carried out daily by diabetic patients themselves.

For many years the use of alkaline copper solutions have been a standard test toindicate the presence of reducing carbohydrates in aqueous solution, the color changes involved permitting both qualitative and quantitative indications. From a medical standpoint, perhaps the most important application of such a test procedure is in the determination of glucose in urine, and this is of particular importance for diabetic patients who must gauge their daily dosage of insulin according to urine sugar content. The need for such daily tests by diabetic patients has provided a strong stimulus for the development of more simplified test procedures, which are adapted for use by the patient in his own home.

Tablets are available commercially today, which upon being dissolved in a urine specimen, provide a color indication corresponding to the glucose content of the specimen. While heating of the test specimen is required with laboratory solutions like Fehlings and Benedicts, the commercial tablets contain a large excess of sodium hydroxide for providing the required heating by means of the heat of solution of the sodium hydroxide in water. While this type of tablet has obvious advantages from the standpoint of convenience, it does have a number of defects and limitations, which heretofore have not been satisfactorily overcome.

Sodium hydroxide is an exceedingly hygroscopic substance, requiring the tablets to be packaged in a completely dry atmosphere, and to be protected from contact with atmospheric moisture until they are used. This problem is paricularly acute because in order to supply the necessary heat for the test reaction, it is usually necessary to have over 50% for the tablet composed of sodium hydroxide. 7

Another limitation on the use of sodium hydroxide as an ingredient of the test composition, is that the composition must be distributed in the form of tablets, rather than as powder which would be more easily dissolved in the specimen. This is true because it is almost impossible to maintain sodium hydroxide in the form of a free-flowing powder. On the other hand, the use of sodium hydroxide in tablets is not a complete answer, because the tablets tend to react on their surfaces with protein substances in the urine specimen, such as albumin and mucin, thereby forming coatings on the tablets which interfere with the dissolution ofthe tablet ingredients. The inclusion of effervescent reagents in the tablet has been proposed for the purpose of overcoming thiscoating problem, but such reagents increase the overall cost of the tablets.

Certain other difliculties and inconveniences are associated with the present procedure for home urine testing. Glass test tubes are employed for the specimens, which must be thoroughly cleaned before reuse. Also, it is necessary to compare the color of the test solution on completion of the reaction with a separate color chart, which is easily misplaced.

It is therefore a general object of this invention to provide an improved method and improved means for the determination of the sugar content of urine by diabetic patients themselves. More specifically, it is an object to provide a method and means of the character described which avoids the use of sodium hydroxide or comparable alkali metal hydroxide, while at the same time providing a composition that supplies its own heat for the test reaction when dissolved in water. Still another object is to provide a sugar test composition which can be commercially distributed in the form of a powder, as well as in the form of tablets, and which in either form requires a lesser amount for the test than has heretofore been required. Still another object is to provide an improved disposable vessel adapted for use in testing the sugar content of urine, which eliminates the need for reusable glass test tubes and a separate color comparison chart. Further objects and advantages will appear as the specification proceeds.

Some of the aspects of this invention are illustrated in the accompanying drawing, in which- Fig. 1 is a side sectional view of a disposable sugar testing vessel constructed in accordance with one part of my invention; and Fig. 2, a plan view of an envelope containing a test mixture in powder form which has been formulated in accordance with another part of my invention.

As already indicated, this invention is generally concerned with a test for reducing sugar in aqueous solution of the type in which a measured quantity of the test solution is mixed with a measured quantity of an alkaline solution of a cupric salt,'and then the mixture is heated to reduce the cupric salt to cuprous oxide in proportion to the reducing sugar content. In the case of urine specimens, the reducing sugar is glucose, While alkaline solutions of copper sulfate are usually employed for making the analysis. In one of its aspects, this invention is particularly concerned with the improvement wherein a solid alkali metal alcoholate is introduced into the speci-L men during testing, and the amount thus introduced is regulated to generate sufficient heat by reaction with the Water in the specimen to form the cuprous oxide.

Any alkali metal alcoholate can be used, since this class of compounds reacts violently with water, although sodium methylate is preferred. For example, sodium ethylate or sodium glycerate can be substitutedfor sodium methylate. The lithium alcoholates, depending on their commercial availability, .are quite desirable because of their very low hygroscopicity.

The other reagents employed for the test would in general be the same as taught by the prior art, that is, the water-soluble cupric salt is preferably copper sulfate, and the test solution should be at an alkaline pH. Since alkali metal alcoholates react with water to form alcohols and alkali metal hydroxides, it is not essential that another reagent be used to provide the required alkilinity for the reaction. Thus, a mixture of ingredients for the test need not contain any sodium hydroxide or other alkali metal hydroxide.

The test solution should also preferably contain a buffer salt which does not interfere with the test reaction. Best results are obtained with water-soluble compounds providing either tartrate or .citrate ions, and this would include not only salts like sodium citrate and sodium tartrate, but also their corresponding namely, tartaric and citric acids, since the acids would be neutralized to form the salts by the alkali metal More specifically, this invention in its method aspect is concerned with the testing for sugar content of urine,

acids, 1

wherein there is introduced into the aqueous test specimen a predetermined quantity of a mixture of solid reagents including a water-soluble cupric salt, an alkali metal alcoholate, and a water-soluble compound providing either tartrate or citrate ions. This mixture is then dissolved in the aqueous solution and at the same time the solution is heated by the reaction of the alkali metal alcoholatewith the water of the solution. It will be understood that a sufficient quantity of the alkali metal alcoholate should be employed to heat the water to a temperaturesufficiently high to convert the cupric salt to cuprous oxide.

One of the important advantages of test compositions formulated in accordance with the present invention is that such compositions can be distributed either in the form of tablets or as a free-flowing powder. In either case, the composition should of course be in a solid, dry form. For example, powdered or finelydivided measured quantities of copper sulfate, sodium methylate, and a suitable buffer, such as sodium tartrate, sodium citrate, tartaric acid, citric acid and other buffers of comparable properties, can be mixed together to form a free-flowing powder, which can then be packaged as illustrated in Fig. 2, where designates an aluminum foil packet consisting of two sheets of aluminum foil crimped together around the edges. As shown in Fig. 2, the packet 10 is broken away to disclose the powdered composition 11 therein, which by tearing a corner of the packet can be intrduced into a test specimen. Alternatively, such compositions can be compressed to form tablets of smaller size than has heretofore been necessary for a similar purpose. It will be understood that other specific ingredients can be substituted, as has already been discussed.

In another of its aspects, this invention is concerned with a disposable vessel adapted for use in testing the sugar content of urine, such a vessel being illustrated in Fig. l of the drawing. In the illustration given, the test vessel consists of a cup 12 formed of a flexible water-retaining sheet material having a water-soluble coating 13 on the lower part of its inside surface. Preferably, cup 12 is formed of water-retaining paper and has a conical shape, as shown.

Coating 13 can contain various ingredients, but it should include a water-soluble cupric salt as one of the essential ingredients, and it preferably also includes a water-soluble compound providing either tartrate or citrate ions in aqueous solution. For example, coating 13 can be composed of a mixture of copper sulfate and sodium tartrate. It can beapplied to the interior of cup 12 by any suitable procedure, such as adding a small amount of water to a mixture of the coating ingredients to form a paste, and then spreading the paste over the interior surfaces of the cup. The coating can then be air-dried, or dried by heating. In this way a predetermined. quantity ofthe test reagents can be included within the disposable vessel, while being readily available for carrying out the test. In using such a disposable vessel, a measured quantity of the specimen would be introduced, followed by a sulficient amount of analkali metal alcoholate to heat the solution to near the boiling point. The violent reaction of the alkali metal alcoholate with the water has the further advantage of promoting the dissolution of the material in the coating layer on the inside of the cup, and thus gives assurance that uniform test results will be obtained.

It is also preferred to provide the disposable test essel with a horizontally-extending indicia 14, as illustrated in Fig. l, for indicating the desired liquid level, and thereby making it unnecessary to measure the test specimen prior to its introduction into cup 12. Also, the upper portion of the inner walls of the cup can have colored panels impressed thereon, such as panels 15, the various panels showing respectively the colors core 4 responding to a particular sugar content, say, from O to 2%, as illustrated.

This invention is further illustrated by the following specific examples:

Example I A free-flowing powder for use in urine sugar testing can be prepared by mixing together powdered copper sulfate, sodium methylate, and sodium tartrate in the proportions indicated below:

Ingredients: Parts by weight Copper sulfate 1 Sodium methylate 5 Sodium tartrate 7 The above compostion can be either packaged in 2 /2 grain portions in powdered form, or can first be compressed into 2 /2 grain tablets. In either case, the 2 /2 grain portion of the composition would be used for a single test by introducing this amount of the composition into from 10 to. 15 drops of liquid, which can consist of 5 drops of urine mixed with 10 drops of water. The test can also be carried out in the way described by using only 5 drops of urine and omitting the water because of the small quantity of the composition employed. The color of the resulting solution will be proportional to the glucose content of the urine, ranging from dark blue for no glucose content to orange or brown for a high glucose content, with intermediate shades of green, olive green, and tan.

Example II A coating composition can be prepared by mixing 1 part by weight of powdered copper sulfate with 10 parts by weight of sodium citrate, and then adding sufficient Water to form a paste. This paste is then applied to the interior of a series of paper cups to form coatings thereon of the type illustrated in Fig. 1. For example, about 1.5 grains on a dry basis of the mixture can be applied as a coating on each container. In using such containers for testing, 15 drops of the specimen could be added, consisting of 10 drops of water and 5 drops of urine. Then from 1 to 2 grains of sodium methylate would be added to heat the test solution whilebringing about the dissolution of the coating material, and thereby completing the test. As a final step, the color comparison would be made as described in Example 1.

While in the foregoing specification this invention has been described in relation to certain specific embodiments thereof and a number of details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the various aspects of this invention are susceptible to other embodiments, and that many of the details set forth herein can be varied without departing from the basic principles of the invention.

I claim:

1. In the testing. of an aqueous specimen for sugar content wherein the Specimen is heated in the presence of a water-soluble cupric salt at an alkaline pH to form cuprous oxide in proportion to the reducing sugar content, the improvement comprising introducing into said specimen during said testing a solid alkali metal alcoholate, and regulating the amount of said alcoholate thus introduced to generate sufficient heat by reaction with the water in said specimen to form said cuprous oxide.

2. The improvement of claim 1 in which said alkali metal alcoholate is sodium methylate.

3. The method of testing for the sugar content of urine, comprising introducing into an aqueous solution a predetermined quantity of a mixture of solid reagents including a water-soluble cupric salt and an alkali metal alcoholate, said solution containing a predetermined quantity of the urine to be tested, dissolving said cupric salt in the aqueous solution, and at the same time beating said solution by reacting said alkali metal alcoholate with the water 5; said solution, said solution being heated by said reaction to a temperature sufiiciently high to convert said cupric salt to cuprous oxide in proportion to the reducing sugar content of said solution.

4. The method of claim 3 in which said cupric salt is copper sulfate, said alkali metal alcoholate is sodium methylate, and in which said mixture also includes a water-soluble compound providing ions selected from the group consisting of tartrate and citrate ions.

5. The method of testing the sugar content of urine, comprising introducing a urine specimen into a disposable vessel having a water-soluble coating on at least the lower part of its inside surface, said coating including a water-soluble cupric salt as one of the essential ingredients thereof, and also introducing into said vessel a solid alkali metal alcoholate in an amount suflicient to violently agitate said specimen, thereby dissolving a substantial portion of said water-soluble coating in said specimen, and at the same time generating sufiicient heat by reaction with the water in said specimen to form cuprous oxide.

6. A sugar test composition in solid, dry form, comprising a mixture of one part by weight of a water soluble cupric salt and substantially five parts by weight of an alkali metal alcoholate.

7. A sugar test composition in solid, dry form, com prising a mixture of one part by weight of a water soluble cupric salt, substantially five parts by weight of an alkali metal alcoholate, and approximately seven parts by weight of a water soluble compound providing ions selected from the group consisting of tartrate and citrate ions.

References Cited in the file of this patent UNITED STATES PATENTS 1,543,961 Zoeren June 30, 1925 2,370,683 Palma Mar. 6, 1945 2,452,385 Merckel Oct. 26, 1948 2,633,410 Beckley Mar. 31, 1953 

1. IN THE TESTING OF AN AQUEOUS SPECIMEN FOR SUGAR CONTENT WHEREIN THE SPECIMEN IS HEATED IN THE PRESENCE OF A WATER-SOLUBLE CUPRIC SALT AT AN ALKALINE PH TO FORM CUPROUS OXIDE IN PROPORTION TO THE REDUCEING SUGAR CONTENT, THE IMPROVEMENT COMPRISING INTRODUCING INTO SAID SPECIMEN DURING SAID TESTING A SOLID ALKALI METAL ALCOHOLATE, AND REGULATING THE AMOUNT OF SAID ALCOHOLATE THUS INTRODUCED TO GENERATE SUFFICIENT HEAT BY REACTION WITH THE WATER IN SAID SPECIMEN TO FORM SAID CUPROUS OXIDE. 